Conventionally, a silicon monomer such as SiH4 (monosilane), SiHCl3 (trichlorosilane), and SiCl4 (tetrachlorosilane) as a raw material for a silicon wafer, and a production method thereof have been known; however, in recent years, with the development of electronic technology, higher-order silane such as Si2H6 (disilane) receives attention as a material with which a chemical vapor deposition method (CVD method) for forming a film such as an amorphous silicon film or a silicon oxide film on a substrate is performed at a low temperature at a high speed, and thus chloropolysilane such as Si2Cl6 grows in demand as a material for the higher-order silane, so that an efficient production method thereof is desired.
For example, Patent Document 1 discloses a method for producing SiCl4 (tetrachlorosilane) by reacting Cl2 with Si obtained from a residue of high purity silicon with the use of a gas-phase fluidized-bed reactor. Patent Document 1 describes providing in the reactor a dust collector for collecting Si particles to be transported to the outside of the reactor, but does not describes that higher-order chloride such as chloropolysilane could be generated by the reaction between Si and Cl2. Thus, without assuming generation of a product other than SiCl4, Patent Document 1 does not refer to possible problems such as condensation or precipitation of a high-boiling higher-order chloride and blockage in the reactor with the chloride at all. Patent Document 1 does not refer to measures against the problems, either.
Patent Document 2 discloses that chloropolysilane is efficiently obtained with the use of copper catalyst or a copper compound catalyst in a reaction of Si with Cl2; however, disclosed is only a producing method using a fixed-bed reactor. Thus, Patent Document 2 does not refer to problems that could arise in a fluidized-bed reactor such as how to trap powders to be conveyed to the outside of the reactor or how to prevent blockage in the reactor with a high-boiling higher-order chloride.
Patent Document 3 discloses a method for producing SiHCl3 (trichlorosilane) by the reaction of metallic silicon powders with HCl gas. A gas phase fluidized-bed reactor is used for the reaction. In the reactor, the metallic silicon powders react with the HCl gas supplied from the bottom of the reactor while fluidize by the gas. SiHCl3 is produced by the reaction. Patent Document 3 also describes separating coarse particles from a reaction fluid containing SiHCl3 discharged from the reactor and returning the coarse particles into the reactor, while filtering out fine particles in the reaction fluid.
One of the significant differences of Patent Document 3 from Patent Documents 1 and 2 is that the HCl gas is used for the reaction in Patent Document 3. Since SiHCl3 is generated stoichiometrically in the reaction, there is no possibility that high-boiling higher-order chloride generated causes a blockage in the reactor; however, unreacted coarse silicon particles and fine particles of chlorides as impurities are both generated in the reaction. Patent Document 3 describes that these particles are separately trapped with the combined use of a separating means for a coarse particle such as a cyclone, and a filter. The unreacted silicon particles trapped are recycled as a reacting material.